Craniosynostoses are a group of congenital disorders which involve the premature fusion of one or more of the cranial sutures, causing cessation or distortion of cranial growth. Increased intracranial pressure i the most critical complication, often resulting in poor intellectual development as well as alterations in vision. The prevalence of these disorders is 1:1000 live births and they can occur alone, or in association with craniofacial syndromes, such as Crouzon's or Apert's. To allowed or adequate cranial growth and brain development, excision of the fused suture(s) is the treatment of choice. Unfortunately, re-ossification of the excised suture is common and necessitates several surgical procedures throughout childhood. A therapeutic agent which could prevent re-ossification of the excised sutures by transiently blocking osteogenesis would be an effective adjunct to surgery. This study will investigate the effect on re-ossification utilizing the unique combination of collagen gel and an anti-osteogenic agent delivered directly to the suture site. Studies outlined in Specific Aim 1 will identify agents that prevent suture fusion. Fibronectin (FN), an extracellular matrix molecule, has been shown to play an essential role in calvarial osteoblast osteogenesis. The FN antagonists anti-FN antibodies, soluble cell-binding FN fragments and anti- FN receptor antibodies have been shown to selectively and reversibly block osteogenesis. A well-characterized rat calvarial organ culture will be used to determine if these FN antagonists can prevent re-ossification of cranial sutures. The antagonists will be combined with a collagen gel and implanted into the site of excised frontal sutures of 15 day old rat calvariae in organ culture. Morphometric and histological analysis will evaluate sutural morphology and ossification after 0,5, 10, 20 and 30 days in culture. In addition reversal studies will be conducted to determine if treated sutures retain the capacity to fuse following removal of the FN antagonist and collagen gel. The FN antagonist which can best demonstrate reversible inhibition of suture fusion and retention in the collagen gel will be selected for further characterization. Studies in Aim 2 will investigate the anti-osteogenic mechanism of the selected antagonist from Aim 1. Biochemical and molecular assays will assess inhibition of collagen synthesis, osteoblast differentiation, tissue mineralization and cell viability. The studies proposed here will extend the novel data from previous FN cell cultured studies into a more complex calvarial organ culture system. The selection and characterization of an anti-osteogenic FN antagonist in organ culture will provide strong data to support a future proposal for animal studies. Together, these studies will provide important data which could be used to develop new therapeutic adjuncts in the treatment of craniosynostosis.